1. Field of the Invention
The present invention relates to subsurface well equipment in wellbores having a plurality of production tubing strings and, more particularly, to an apparatus for selection of and entry into a particular tubing string by a re-entry device and a related method.
2. Description of the Related Art
Wells having a central bore and lateral branches extending therefrom, and extending into the hydrocarbon producing subterranean formations are well known as "multilateral wells." Also well known in the art are "dual completions," i.e., wells having a plurality of production tubing strings to carry hydrocarbons from subterranean producing zones via discrete and corresponding tubing strings to the surface of the earth. During the life of a well, remediation of one or more producing zones may be required by a technique commonly known as "wireline or coiled tubing intervention," whereby a well known intervention tool is lowered into the well on a small diameter wire or coiled tubing, and a service operation is performed that improves production, collects data, or performs operations critical to the well's performance.
Well known to those of ordinary skill in the art are two basic types of "wireline" tools: electric line (commonly called "e-line") and slickline. E-line tools require a multi-functional wire, whereby in addition to suspending and conveying the tool to a specific location in a well, the e-line is also used to transmit power from the surface to the intervention tool and/or transmit data between the surface and the intervention tool. Conversely, slickline tools use a simple wire to suspend and convey the tool to its selected location, and are designed to require no electrical power from the surface to perform their designed function. One of ordinary skill in the art will immediately appreciate the difficulty of both types of wireline tools in selecting a particular branch lateral wellbore extending from a central wellbore, where at least one lateral branch is present. As noted above, coiled tubing, as opposed to wireline, is also commonly used to run intervention tools into wells.
Well known in the art of completion techniques are methods and associated completion equipment for "tieing-back" or connecting two production tubing strings, attached to a permanent downhole tubing hanger, to a subsea christmas tree. The ability to manipulate a tie-back string so that it reliably and accurately aligns with one of a plurality of production strings located a distance in the well below the christmas tree illustrates the importance of downhole orientation. It is essential to well operations to be able to select and interconnect the production tubing strings to a respective location and orientation of flow lines in the tree. The tie-back string is essentially a spool connecting the tubing hanger to the christmas tree, and enables discrimination between tubing fixed in the downhole tubing hanger, and flow ports in the christmas tree.
In most dual completions, a first length of production tubing extends from a first producing zone to the tree and a second length of production tubing extends from a second producing zone to the tree. Therefore, a selection of the desired tubing string for intervention is often as simple as inserting the intervention tool directly or indirectly into the tubing via a device known as a "lubricator." The lubricator sealably connects to the tree, and allows insertion of the intervention tool in the wellbore while simultaneously preventing the flow of pressurized wellbore fluids into the surrounding environment. In the case of multiple tubing strings and flow lines, the lubricator must be connected separately to each flow line if intervention techniques are to be employed.
When remediation or service is required in multilateral and dual completion wells, the operator must select and enter the proper branch of the well, or completion string, and simply and reliably enable a service tool to be conveyed therein. An object of the present invention is to enable the operator to simply and easily make a configurational modification to the intervention tool at the surface prior to deployment. This modification enables the invention to enter a selected branch of a multilateral wellbore or a dual completion. Another object of the invention is to simplify the configuration of the completion. By eliminating expensive components, initial costs can be minimized, thereby making the well more cost effective to deploy and operate.
There is a need for a selective re-entry tool for use in wells having a plurality of tubing strings and which has the ability to discriminate between the strings and to reliably orient a service tool string for entry into a desired lateral branch. This need may exist, for example, where the tubing entry point is at a depth below the wellhead, possibly very deep in the well. There is also a need to accomplish discrimination and selection functions with a simple surface modification to the intervention tool that will result in cost savings in the design, operation, and implementation of the well. Further, it is desirable to eliminate the need for a "tie-back" tubing string for intervention operations and the high costs associated with building and deploying it.